Well i know that if you drink cold water all day the body has to burn calories to bring it up to body temperature, it's one of those little tips they teach you in the multitude of diet books out there hehe I don't think you burn many but you do burn a little more than usual so I expect if you spend your time outside in the cold the body has to work harder to maintain your body temperature also and with the same effect. Mind you, I don't think I want to go out in the freezing cold to test that theory hehe